Answer:
42 teaspoons of vinegar should be used
Explanation:
This question is solved by proportions, using a rule of three.
4 teaspoons of vegetable oil and 12 teaspoons of vinegar. 14 teaspoons of vegetable oil were used
So
4 teaspoons of vegetable oil - 12 teaspoons of vinegar
14 teaspoons of vegetable oil - x teaspoons of vinegar
So
Dividing both sides by 4:
42 teaspoons of vinegar should be used